1. Field of Invention
The present invention relates to methods and devices for molding cast parts and more particularly for the cooling of foundry sand in connection with the molding process.
2. Brief Description of the Prior Art
In the manufacture of cast iron parts the patterns for the cast parts are molded under high pressure in sand molds and molten iron is poured into the hollow spaces. After solidification of the iron the cast parts are removed from the mold and the foundry sand is prepared and used again for producing a mold. Through contact with the molten metal the foundry sand has become very hot in places so that cooling is imperative before re-use.
Various methods are known for cooling used sand.
Among the most common methods is the breaking up and flowing through of the sand with air. For this, extremely large-sized devices with very large operational capacity are needed for cooling down the very unevenly heated sand particles to a useable temperature. The heated cooling air is mixed with dust and has to be cleaned in large volume dust extraction installation. The disadvantages of this method are the large space and energy requirements.
In OS 30 06 552 a cooling apparatus is described wherein 2 containers are alternately filled with wetted hot used sand and then placed in a vacuum. The moisture in the sand evaporates and draws the heat of evaporation from the sand. It is disadvantageous with this method that the intermittent operation requires 2 evacuating containers and the vacuum in the very large containers must be constantly produced and terminated. The energy costs and space requirements of such an installation are therefore very considerable.
A foundry sand mixer is described in P 29 52 403, the mixing area of which is evacuated during the mixing process so that in this case also, evaporation heat is dissipated. In this method too, the proportion of evacuation volume to the quantity of sand is very unfavourable, as in this case also the vacuum has to be produced and terminated with each mixing cycle. The normal mixing cycle must, in addition, be significantly lengthened so that here again, energy and investment costs work out unfavorably.